Neurophysiology Services Provided

Around 11,000 tests per year are carried out here in Southampton and also in peripheral clinics run by our Clinical Physiologists at Salisbury and Chichester district hospitals. Patients range in age from the premature baby to the elderly. Referrals come via many routes including neurology, orthopaedics, paediatricians and general practice from all over Hampshire, the Isle of Wight and the Channel Islands.

Clinical Physiologists carry out many tests, while Consultant Neurophysiologists and Specialist Registrars perform more invasive procedures.

The following tests are performed here:

1. Electroencephalogram (EEG)
   This is a recording of the electrical activity (i.e. brainwaves) produced continuously by the cerebral cortex. Small electrodes are attached to the scalp to make the recording. The patient lies quietly with eyes closed for 20 minutes while the recording is made. Provocative techniques of 3 minutes hyperventilation and exposure to a bright flashing light are sometimes included to add further diagnostic information. In some cases the test may be repeated after 24 hours sleep deprivation. It may also be necessary to capture attacks by attaching electrodes and a portable recorder for periods upto 72 hours. Common conditions investigated are epilepsy, encephalopathies and dementias.
2. Video Telemetry
   Up to 5 days concurrent EEG and time-locked digital video are recorded in our purpose-built suite to examine both electrographic and clinical semiology of attacks for diagnostic purposes. Patients are investigated to try and diagnose the type of seizures they are having and also their suitability for epilepsy surgery.
3. Intracranial Electrodes
   For pre-surgical patients, it is may be necessary to record directly from the cerebral cortex using surgically implanted depth electrodes or subdural grids. Sometimes electrical cortical stimulation is required to map the brain function under the grid. This extended monitoring is then followed by surgery to remove the electrodes and perform resective surgery at the same time.
4. Nerve Conduction
   Aids the diagnosis of nerve entrapments and neuropathies. A common condition we test for is carpal tunnel syndrome, in which the median nerve (supplying Digits 1-3, and half of Digit 4) becomes compressed against the transverse carpal ligament, giving rise to pain, weakness and numbness in the affected hand. Nerve impulses are recorded travelling along motor or sensory nerves in the hands and arms by applying electrical pulses directly over the known course of the nerve and recording the impulses as they pass along further up the nerve. Calculations are made based upon the length of the nerve and arrival time of the nerve impulse to determine the conduction velocity of each nerve. An affected nerve may conduct more slowly and at a lower voltage than normal.
5. Electromyography
   Conducted by Consultant and Specialist Registrar Neurophysiology medical staff. A needle electrode inserted in a muscle will "listen" to electrical activity produced by a contracting muscle and will help to determine if weakness is caused by nerve damage or muscle disease. Conditions diagnosed include Motor Neuron Disease, myopathy and neuropathy.
6. Evoked Potentials (EPs)
   These are tiny signals produced by the brain in response to the arrival of a nerve impulse. Using 6 to 8 scalp electrodes we determine how long after a stimulus it takes for the signal to be registered in the brain. EPs are useful in the non-invasive diagnosis of multiple sclerosis and lumbar radiculopathy among other conditions. A number of different methods are used according to the system under test: 
   
   
   • Visual Evoked Potentials
     For the optic nerve the patient watches a monitor showing a chequerboard pattern with a reversing black and white square pattern. This is a simple stimulus for the visual cortex and the time taken for the impulse to travel from eye to brain is measured.
   • Brainstem Evoked Potentials
     Gives information about conduction times through the auditory nerves and brainstem using a fast click stimulus via headphones.
   • Sensory Evoked Potentials
     For sensory pathways from the upper or lower limbs, through the spinal cord to the brain. Small electrical pulses are applied over a nerve in the affected limb.
   • Spinal Cord Monitoring
     Clinical Physiologists record sensory evoked potentials continuously throughout surgery for correction of scoliosis in order to provide an early warning of any potentially reversible damage to the spinal cord. The Clinical Physiologists can immediately inform the surgeon of any problem (e.g. reduction in amplitude of EP), thus reducing the risk of paralysis, and making surgery safer.
   • Brainstem auditary evoked potentials (BAEPs) for hemifacial spasm surgery
     BAEPs are used to protect the integrity of the 8^th nerve during neurosurgical procedures for microvascular decompression for hemifacial spasm. The Clinical Physiologists can immediately inform the surgeon of any potential problem, reducing the risk of deafness and making surgery safer.

7. Visual Fields

   Wessex Neurological Centre referrals only. A non-invasive technique used to map out the pattern and extent of visual impairment of patients with neurological conditions such as tumours, strokes or raised intracranial pressure. The patient sits in a darkened room looking at a white background, onto which are projected carefully calibrated light stimuli and responds by pressing a button. The results are plotted on a chart for each eye.